The effects of embedding in water-soluble plastics on the final dimensions of liver sections

This paper describes the morphometric changes liver samples undergo in the course of fixation, dehydration, infiltration and embedding in different mixtures of water-soluble plastics. The plastics used were: three different mixtures of glycolmethacrylate (GMA) and the commercially available material JB4. Buffered formaldehyde fixation did not produce significant morphometric changes in the liver specimens. Dehydration obviously affects the volume of the liver specimen (linear shrinkage about 9.3%). The dehydration is followed by an infiltration phase. During this phase a slight swelling (linear, 2-5%) occurs. The final polymerization of the plastic resulted in a further linear shrinkage of 1-2%. The influence of different technical factors on the stretching of sections of pure plastic and of plastic embedded liver appeared to be considerable. The difference in stretching between 2 and 3 micron sections has been studied. A significant influence of temperature upon section stretching was noted. Sections of all plastic mixtures stretched at a temperature of 293 K showed 3% more linear stretch than at a temperature of 333 K. Differences between the four plastic mixtures are discussed. Correction factors must be used in morphometrical and stereological investigations (see for review: Weibel, 1979). It was concluded that in the application of water-soluble plastics as embedding media it is essential to apply a standardized procedure, particularly in the cutting and stretching phase.